Low density, low temperature plasmas generated and sustained indefinitely using a focused microwave beam

A focused microwave beam is used to generate and sustain a low temperature, low density plasmas for long periods of time. The drive beam operates at a frequency of 4.7 GHz with a total power of 5–10 kW. An innovative design for the microwave transparent windows allows the beam to enter and exit the pressure vessel with insignificant reflections from the metallic vessel walls. The beam-plasma interaction therefore approximates free-space conditions.